Problems with DNS in the server

The company applied for a fixed IP from Unicom, and then set up a Web server in its own room, the server needs its own DNS to access the Internet, the server (CentOS) configured on the DNS, site access is not a problem.
But I'm going to use a file_get_contents or something like that on this server, and I'll report an error.

PHP Warning:  file_get_contents():  

Basic OK is the problem of DNS! How to solve this problem? To find Unicom?

Reply content:

The company applied for a fixed IP from Unicom, and then set up a Web server in its own room, the server needs its own DNS to access the Internet, the server (CentOS) configured on the DNS, site access is not a problem.
But I'm going to use a file_get_contents or something like that on this server, and I'll report an error.

PHP Warning:  file_get_contents():  

Basic OK is the problem of DNS! How to solve this problem? To find Unicom?

Restart Apache after modify/etc/resolve.conf

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